Okay, I responded to your first thread, but now that I understand your question, I'll try again. I'll describe the battery.
The battery itself is about half the length of an AA battery (the battery is even called a 1/2 AA). The enclosure that it is in is black, and it's a little big bigger than the battery itself. The lid (which has a "window" on the top, you can see the battery inside) has a small tab on each end. You'll probably need a slotted screwdriver to pry the tab open (be careful, don't break it). Make note of which way the battery is seated in the enclosure, so you don't put it in backwards.
The enclosure is usually near the border of the motherboard (not in the middle), but I'm not exactly sure of the location in the IIcx.
Hope this helps,